Pyridopyrimidinone antianginal agents

ABSTRACT

Compounds of the formula ##STR1## and pharmaceutically acceptable salts thereof, wherein R 1  is H, C 1  -C 4  alkyl CN or CONR 4  R 5  ; R 2  is C 2  -C 4  alkyl; R 3  is SO 2  NR 6  R 7 , NO 2 , NH 2 , NHCOR 8  NHSO 2  R 8  or N(SO 2  R 8 ) 2  ; R 4  and R 5  are each independently selected from H and C 1  -C 4  alkyl; R 6  and R 7  are each independently selected from H and C 1  -C 4  alkyl optionally substituted with CO 2  R 9 , OH, pyridyl 5-isoxazolin-3-onyl, morpholino or 1-imidazolidin-2-onyl; or together with the nitrogen atom to which they are attached form a pyrrolidino, piperidino, morpholino, 1-pyrazolyl or 4-(NR 10 )-1-piperazinyl group wherein any of said groups may optionally be substituted with one or two substituents selected from C 1  -C 4  alkyl, CO 2  R 9 , NH 2  and OH; R 8  is C 1  -C 4  alkyl or pyridyl; R 9  is H or C 1  -C 4  alkyl; and R 10  is H, C 1  -C 4  alkyl or (hydroxy) C 2  -C 3  alkyl; are selected cGMP PDE inhibitors useful in the treatment of, inter alia, cardiovascular disorders such as angina, hypertension, heart failure and atherosclerosis.

This is the national stage under 35 U.S.C. §371(c) of InternalApplication No. PCT/EP93/02097, having an international filing data ofAug. 4, 1993, which was oridingally filed Aug. 28, 1992 as Great BritainPatent Application No. 9218322.7.

This invention relates to a series of pyrido[3,2-d]pyrimidin-4-ones,which are potent and selective inhibitors of cyclic guanosine3',5'-monophosphate phosphodiesterase (cGMP PDE), having utility in avariety of therapeutic areas including the treatment of cardiovasculardisorders such as angina, hypertension, heart failure andatherosclerosis.

The compounds of the invention exhibit selectivity for inhibition ofcGMP PDEs rather than cyclic adenosine 3',5'-monophosphatephosphodiesterases (cAMP PDEs) and, as a consequence of this selectivePDE inhibition, cGMP levels are elevated, which in turn can give rise tobeneficial anti-platelet, anti-neutrophil, anti-vasospastic andvasodilatory activity, as well as potentiation of the effects ofendothelium-derived relaxing factor (EDRF) and nitrovasodilators. Thusthe compounds have utility in the treatment of a number of disorders,including stable, unstable and variant (Prinzmental) angina,hypertension, pulmonary hypertension, congestive heart failure,atherosclerosis, conditions of reduced blood vessel patency e.g.post-percutaneous transluminal coronary angioplasty (post-PTCA),peripheral vascular disease, stroke, bronchitis, allergic asthma,chronic asthma, allergic rhinitis, glaucoma, and diseases characterisedby disorders of gut motility, e.g. irritable bowel syndrome (IBS).

European patent application EP-A-0347146 discloses certainpyrido[3,2-d]pyrimidin-4-ones which, unlike the compounds of the presentinvention, contain a monosubstituted phenyl moiety at the 2-position ofthe said heterobicyclic system. These compounds are reported to beselective cGMP PDE inhibitors with bronchodilator and vasodilatoractivity of value in combatting asthma, bronchitis, angina, hypertensionand congestive heart failure. The compounds of the present inventioncontain a 2,5-disubstituted phenyl moiety at the 2-position of thepyrido[3,2-d]pyrimidin-4-one bicyclic system and are significantly morepotent cGMP PDE inhibitors than the previously mentioned prior artcompounds.

The compounds of the present invention have the formula (I): ##STR2##and pharmaceutically acceptable salts thereof, wherein R¹ is H, C₁ -C₄alkyl, CN or CONR⁴ R⁵ ;

R² is C₂ -C₄ alkyl;

R³ is SO₂ NR⁶ R⁷, NO₂, NH₂, NHCOR⁸, NHSO₂ R⁸ or N(SO₂ R⁸)₂ ;

R⁴ and R⁵ are each independently selected from

H and C₁ -C₄ alkyl;

R⁶ and R⁷ are each independently selected from

H and C₁ -C₄ alkyl optionally substituted with CO₂ R⁹, OH pyridyl5-isoxazolin-3-onyl, morpholino or 1-imidazolidin-2-onyl; or togetherwith the nitrogen atom to which they are attached form a pyrrolidino,piperidino, morpholino, 1-pyrazolyl or 4-(NR¹⁰)-1-piperazinyl groupwherein any of said groups may optionally be substituted with one or twosubstituents selected from C₁ -C₄ alkyl, CO₂ R⁹, NH₂ and OH;

R⁸ is C₁ -C₄ alkyl or pyridyl;

R⁹ is H or C₁ -C₄ alkyl;

and R¹⁰ is H, C₁ -C₄ alkyl or (hydroxy) C₂ -C₃ alkyl.

In the above definition, unless otherwise indicated, alkyl groups havingthree or more carbon atoms may be straight chain or branched chain.

The compounds of formula (I) may contain one or more asymmetric centresand thus they can exist as stereoisomers, i.e. as enantiomers or asdiastereoisomers. The invention includes both mixtures thereof and theseparated individual stereoisomers.

The compounds of formula (I) may also exist in tautomeric forms and theinvention includes both mixtures thereof and the separated individualtautomers.

Also included in the invention are radiolabelled derivatives ofcompounds of formula (I) which are suitable for biological studies.

The pharmaceutically acceptable salts of the compounds of formula (I)which contain a basic centre are, for example, non-toxic acid additionsalts formed with inorganic acids such as hydrochloric, hydrobromic,sulphuric and phosphoric acid, with organo-carboxylic acids, or withorgano-sulphonic acids. Compounds of formula (I) can also providepharmaceutically acceptable metal salts, in particular non-toxic alkalimetal salts, with bases. Examples include the sodium and potassiumsalts. For a review on suitable pharmaceutical salts, see J. Pharm,Sci., 1977, 66, 1.

A preferred group of compounds of formula (I) is that wherein R¹ is H,n-propyl, CN or CONH₂ ; R² is ethyl; R³ is SO₂ NR⁶ R⁷, NO₂, NH₂,NHCOCH(CH₃)₂, NHSO₂ CH(CH₃)₂, NHSO₂ (3-pyridyl) or N[SO₂ (3-pyridyl) ]₂; R⁶ is H, methyl or 2-hydroxyethyl; R⁷ is methyl optionally substitutedwith 2-pyridyl or 5-isoxazolin-3-onyl, or ethyl 2-substituted with OH,CO₂ CH₂ CH₃, morpholino or 1-imidazolidin-2-onyl, or R⁶ and R⁷ togetherwith the nitrogen atom to which they are attached form a (4-CO₂R⁹)piperidino, 5-amino-3-hydroxy-1-pyrazolyl or 4-(NR¹⁰)-1-piperazinylgroup; R⁹ is H or ethyl; and R¹⁰ is H, methyl or 2-hydroxyethyl.

A particularly preferred group of compounds of formula (I) is thatwherein R¹ is n-propyl or CN; R⁹ is ethyl; R³ is SO₂ NR⁶ R⁷, NHSO₂CH(CH₃)₂, NHSO₂ (3-pyridyl) or N[SO₂ (3-pyridyl)]₂ ; R⁶ is H or methyl;R⁷ is methyl, or ethyl 2-substituted with CO₂ CH₂ CH₃, morpholino or1-imidazolidin-2-onyl, or R⁶ and R⁷ together with the nitrogen atom towhich they are attached form a (4-CO₂ R⁹) piperidino or4-(NR¹⁰)-1-piperazinyl group; R⁹ is H or ethyl; and R¹⁰ is H, methyl or2-hydroxyethyl.

Especially preferred individual compounds of the invention include:

2-[2-ethoxy-5-(4-ethoxycarbonylpiperidino-sulphonyl)phenyl]-8-n-propylpyrido[3,2-d]pyrimidin-4(3H)-one;

2-[5-(4-carboxypiperidinosulphonyl)-2-ethoxyphenyl]-8-n-propylpyrido[3,2-d]pyrimidin-4(3H)-one;

2-{2-ethoxy-5-[4-(2-hydroxyethyl)-1-piperazinyl-sulphonyl]phenyl}-8-n-propylpyrido[3,2-d]pyrimidin-4(3H)-one;

and2-{2-ethoxy-5-[(bis-3-pyridylsulphonyl)amino]-phenyl}-8-n-propylpyrido[3,2-d]pyrimidin-4(3H)-one.

In another aspect, the present invention provides processes for thepreparation of compounds of formula (I) and pharmaceutically acceptablesalts thereof, as hereinafter described. Depending on the nature of R³,the compounds of formula (I) may be prepared by a variety of methodsfrom a compound of formula (II): ##STR3## wherein R¹ and R² are aspreviously defined for formula (I).

(A) A compound of formula (I) wherein R³ is SO₂ NR⁶ R⁷, wherein R⁶ andR⁷ are as previously defined, may be obtained from a compound of formula(II) via the intermediacy of a sulphonyl halide of formula (III):##STR4## wherein Z is halo, preferably chloro, and R¹ and R² are aspreviously defined for formula (II), by reaction with an amine offormula (IV):

    HNR.sup.6 R.sup.7                                          (IV)

wherein R⁶ and R⁷ are as previously defined for formula (I). Thereaction is generally carried out at ambient temperature, preferably inthe presence of a solvent, e.g. a C₁ -C₃ alkanol, using about a 3-foldexcess of (IV) to scavenge the acid by-product (HZ) and, in the case ofpiperazine (R¹⁰ is H), also to minimise bis-sulphonamide formation.

Certain of these compounds of formula (I), wherein R¹⁰ is as previouslydefined but not hydrogen, may be prepared directly from thecorresponding 4-N-unsubstituted piperazine analogue, that is theprecursor wherein R¹⁰ is hydrogen, using appropriate standard alkylationprocedures.

A compound of formula (III) is obtainable from (II) by the applicationof known methods for the introduction of a SO₂ Z group into a benzenering; for example, when Z is chloro, by the action of excesschlorosulphonic acid.at from about 0° C. to ambient temperature.

When the SO₂ NR⁶ R⁷ substituent of the required compound of formula (I)contains a CO₂ R⁹ substituent wherein R⁹ is H, the said compound is mostconveniently obtained from the corresponding ester precursor, i.e.wherein R⁹ is C₁ -C₄ alkyl. This may be generally achieved byacid-catalysed or base-catalysed hydrolysis or, more specifically, byprotonolysis, e.g. when R⁹ is t-butyl, by using hydrogen chloride ortrifluoroacetic acid. A typical base-catalysed hydrolysis involves theuse of an alkali metal hydroxide, e.g. sodium hydroxide or potassiumhydroxide, in an aqueous C₁ -C₃ alkanol (preferably ethanol) solventmedium, at from ambient temperature to the reflux temperature of thereaction mixture.

(B) A compound of formula (I) wherein R³ is NO₂ may be obtained from acompound of formula (II) under typical aromatic nitration condition,e.g. using a concentrated nitric acid/concentrated sulphuric acidcombination at from about 0° C. to ambient temperature.

(C) A compound of formula (I) wherein R³ is NH₂ may be obtained from thecorresponding nitroarene precursor described above in (B) by catalytichydrogenation or reduction procedures. For example, hydrogenation may beachieved using a palladium on charcoal or Raney nickel catalyst, in asuitable solvent e.g. ethanol, whilst reduction may be carried out usingabout a 5-fold excess of stannous chloride, in a suitable solvent suchas a C₁ -C₃ alkanol, e.g. ethanol, at the reflux temperature of thereaction mixture.

(D) A compound of formula (I) wherein R³ is NHCOR⁸, wherein R⁸ is aspreviously defined for formula (I), may be obtained from thecorresponding aminoarene precursor described above in (C) by acylationwith either an acyl halide of formula R⁸ COZ, wherein Z is as previouslydefined, or with an acid anhydride of formula (R⁸ CO)₂ O. For example,in the former case, up to about a 50% excess of the acyl halide may beemployed in a suitable solvent, e.g. dichloromethane, in the presence ofa suitable acid acceptor, e.g. triethylamine or pyridine, at from about0° C. to ambient temperature. Alternatively, the reaction may beconducted using pyridine as both solvent and acid acceptor. In thelatter case, reaction of the aminoarene with up to about a 50% excess ofthe required acid anhydride may be effected in a suitable solvent, e.g.pyridine, at from about 0° C. to about 100° C.

(E) A compound of formula (I) wherein R³ is NHSO₂ R⁸ or N(SO₂ R⁸)₂,wherein R⁸ is as previously defined for formula (I), may be obtainedfrom the corresponding aminoarene precursor described above in (C) bysulphonylation with either a sulphonyl halide of formula R⁸ SO₂ Z,wherein Z is as previously defined, or with a sulphonic anhydride offormula (R⁸ SO₂)₂ O, by direct analogy with the acylation processesdescribed above in (D) .

A compound of formula (II) may be prepared from a compound of formula(V): ##STR5## wherein R¹ and R² are as previously defined for formula(II), by the application of known cyclisation methods for pyrimidinonering formation. Thus, for example, the cyclisation may be effected bythe treatment of (V) with a base such as sodium hydroxide or potassiumcarbonate, optionally in the presence of hydrogen peroxide, in anethanol-water medium at the reflux temperature of the reaction mixture.

In alternative cyclisation procedures, compounds of formula (II) may beobtained by treatment of (V) either with polyphosphoric acid at about140° C. or with anhydrous zinc chloride at about 210° C.

More conveniently, a compound of formula (II) wherein R¹ is CONR⁴ and R⁴and R⁵ are as previously defined for formula (I) may be obtained fromthe nitrile precursor, i.e. the corresponding compound of formula (II)wherein R¹ is CN. This may be achieved by firstly hydrolysing thenitrile to the carboxylic acid, e.g. using sodium hydroxide or potassiumhydroxide in an aqueous C₁ -C₃ alkanol (preferably ethanol) solventmedium at about the reflux temperature of the reaction mixture. Next,the carboxylic acid may be converted to the required amide either via anintermediate acyl halide or alternatively-activated form of the acid,such as those.used in amino acid coupling procedures, or via e.g. anintermediate methyl ester or ethyl ester. For example, the acyl chloridemay be generated using oxalyl chloride and a catalytic quantity ofdimethyl-formamide in dichloromethane, and then converted directly tothe amide with an amine of formula HNR⁴ R⁵ (VI) under standardconditions, or the acid may be activated using acarbodiimide/1-hydroxybenzotriazole combination in the presence of (VI)in a suitable solvent such as dichloromethane. Alternatively, the methylester or ethyl ester may be synthesised by replacing (VI) with methanolor ethanol respectively, and then converted to the required amide bytreatment with excess (VI) in a bomb at from about 50° C. to about 100°C.

When R¹ is CONH₂, such a compound of formula (II) can be obtaineddirectly from the said nitrile precursor, e.g. by treatment with 30%aqueous hydrogen peroxide solution and an alkali metal hydroxide(preferably sodium hydroxide) in an aqueous C₁ -C₃ alkanol (preferablyethanol) solvent medium at about the reflux temperature of the reactionmixture.

A compound of formula (V) may be prepared from a compound of formula(VII): ##STR6## wherein R¹ is as previously defined for formula (V), byreaction with a compound of formula (VIII): ##STR7## wherein R² and Zare as previously defined for formula (III).

The reaction is generally carried out using from about 1 to about 2equivalents of (VIII) in the presence of an excess of a tertiary aminesuch as triethylamine or pyridine to act as scavenger for the acidby-product (HZ), optionally in the presence of a catalyst such as4-dimethylaminopyridine, in an inert solvent such as dichloromethane, atfrom about 0° C. to ambient temperature for 2-24 hours. For convenience,pyridine may also be used as solvent.

Compounds of formula (I) may be obtained more directly from a compoundof formula (IX): ##STR8## wherein R², R³ and Z are as previouslydefined, when such acyl halides are readily accessible, by reaction with(VII) and subsequent ring-closure of the product as described above.Clearly this alternative synthetic route will only be appropriate whenR³ is compatible with the reaction conditions obtaining in both steps.

The 3-aminopyridine-2-carboxamides of formula (VII), the acyl halides offormulae (VIII) and (IX), and the intermediates employedfor.introduction of the various R³ substituents into compounds offormula (II) to afford compounds of formula (I), when neithercommercially available nor subsequently described, can be obtainedeither by analogy with the process described in the Preparations sectionor by conventional synthetic procedures, in accordance with standardtextbooks on organic chemistry or literature precedent, from readilyaccessible starting materials using appropriate reagents and reactionconditions.

Moreover, persons skilled in the art will be aware of variations of, andalternatives to, those processes described hereinafter in the Examplesand Preparations sections such that all the compounds defined by formula(I) are obtainable.

The pharmaceutically acceptable acid addition salts of the compounds offormula (I) which contain a basic centre may also be prepared in aconventional manner. For example a solution of the free base is treatedwith the appropriate acid, either neat or in a suitable solvent, and theresulting salt isolated either by filtration or by evaporation undervacuum of the reaction solvent. Pharmaceutically acceptable baseaddition salts can be obtained in an analogous manner by treating asolution of a compound of formula (I) with the appropriate base. Bothtypes of salt may be formed or interconverted using ion-exchange resintechniques.

The biological activities of the compounds of the present invention weredetermined by the following test methods.

Phosphodiesterase activity

Compound affinities for cGMP and cAMP PDEs are assessed by determinationof their IC₅₀ values (the concentration of inhibitor required for 50%inhibition of enzyme activity). The PDE enzymes are isolated from rabbitplatelets and rat kidney, essentially by the method of W. J. Thompson etal. (Biochem., 1971, 10, 311). The calcium/calmodulin(Ca/CAM)--independent cGMP PDE and the cGMP-inhibited cAMP PDE enzymesare obtained from rabbit platelets whilst, of the four major PDE enzymesof the rat kidney, the Ca/CAM-dependent cGMP PDE (fraction I) isisolated. Assays are performed using a modification of the "batch"method of W. J. Thompson and M. M. Appleman (Biochem., 1979, 18, 5228).Results from these tests show that the compounds of the presentinvention are potent and selective inhibitors of Ca/CAM-independent cGMPPDE.

Platelet anti-aggregatory activity

This is assessed by the determination of a compound's ability to inhibitplatelet aggregation in vitro induced by platelet activating factor(PAF), and to potentiate the platelet antiaggregatory action in vitro ofactivators of guanylate cyclase such as nitroprusside and EDRF. Washedplatelets are prepared essentially by the method of J. F. Mustard et al.(Methods in Enzymol., 1989, 169, 3) and aggregation is determined usingstandard turbidimetric techniques as described by G.V.R. Born, (J.Physiol. (Lond), 1962, 162, 67P).

Antihypertensive activity

This is assessed following intravenous or oral administration of acompound to spontaneously hypertensive rats. Blood pressure is recordedvia a cannula implanted in the carotid artery of either conscious oranaesthetised animals.

For administration to man in the curative or prophylactic treatment ofthe disorders identified on page 1, oral dosages of the compounds willgenerally be in the range of from 4-800 mg daily for an average adultpatient (70 kg). Thus for a typical adult patient, individual tablets orcapsules contain from 2-400 mg of active compound, in a suitablepharmaceutically acceptable vehicle or carrier, for administration insingle or multiple doses, once or several times per day. Dosages forintravenous, buccal or sublingual administration will typically bewithin the range of from 1-400 mg per single dose as required. Inpractice the physician will determine the actual dosing regimen whichwill be most suitable for an individual patient and it will vary withthe age, weight and response of the particular patient. The abovedosages are exemplary of the average case but there can be individualinstances in which higher or lower dosage ranges may be merited, andsuch are within the scope of this invention.

For human use, the compounds of the formula (I) can be administeredalone, but will generally be administered in admixture with apharmaceutical carrier selected with regard to the intended route ofadministration and standard pharmaceutical practice. For example, theymay be administered orally, buccally or sublingually, in the form oftablets containing excipients such as starch or lactose, or in capsulesor ovules either alone or in admixture with excipients, or in the formof elixirs or suspensions containing flavouring or colouring agents. Thecompounds may also be injected parenterally, for example intravenously,intramuscularly, subcutaneously or intracoronarily. For parenteraladministration, they are best used in the form of a sterile aqueoussolution which may contain other substances, for example salts, ormonosaccharides such.as mannitol or glucose, to make the solutionisotonic with blood.

Thus the invention provides a pharmaceutical composition comprising acompound of formula (I), or a pharmaceutically acceptable salt thereof,together with a pharmaceutically acceptable diluent or carrier.

The invention also provides a compound of formula (I), or apharmaceutically acceptable salt thereof, or a pharmaceuticalcomposition containing either entity, for use in medicine.

The invention further provides the use of a compound of formula (I), ora pharmaceutically acceptable salt thereof, or a pharmaceuticalcomposition containing either entity, for the manufacture of amedicament for the treatment of stable, unstable and variant(Prinzmetal) angina, hypertension, pulmonary hypertension, congestiveheart failure, atherosclerosis, stroke, peripheral vascular disease,conditions of reduced blood vessel patency e.g. post-PTCA, chronicasthma, bronchitis, allergic asthma, allergic rhinitis, glaucoma, ordiseases characterised by disorders of gut motility, e.g. IBS.

In a further aspect, the invention provides a method of treating orpreventing stable, unstable and variant (Prinzmetal) angina,hypertension, pulmonary hypertension, congestive heart failure,atherosclerosis, stroke, peripheral vascular disease, conditions ofreduced blood vessel patency e.g. post-PTCA, chronic asthma, bronchitis,allergic asthma, allergic rhinitis, glaucoma, or diseases characterisedby disorders of gut motility, e.g. IBS, in a mammal (including a humanbeing), which comprises administering to said mammal a therapeuticallyeffective amount of a compound of formula (I), or a pharmaceuticallyacceptable salt thereof, or a pharmaceutical composition containingeither entity.

The invention also includes any novel intermediates of formulae (II) and(III) disclosed herein.

The syntheses of the compounds of the invention and of the intermediatesfor use therein are illustrated by the following Examples andPreparations. The purity of the compounds was routinely monitored bythin layer chromatography (TLC) using Merck Kieselgel 60 F₂₅₄ plates. ¹H-Nuclear magnetic resonance (NMR) spectra were recorded using either aNicolet QE-300 or a Bruker AC-300 spectrometer and were in all casesconsistent with the proposed structures.

Ambient temperature means 20° C. to 25° C.

EXAMPLE 1

2-[2-Ethoxy-5-(2-morpholinoethylsulphamoyl)phenyl]-8-n-propylprido[3,2,d]pyrimidin-4 (3H) -one

2- (2-Ethoxyphenyl ) -8-n-propylpyrido [3,2-d]pyrimidin-4 (3H) -one(Preparation 8; 1.09 g, 0. 00353 mol) was added portion-wise to stirredchlorosulphonic acid (4 ml) under a nitrogen atmosphere at 0° C. Themixture was stirred at ambient temperature for 18 hours and then addedcautiously to ice/water (100 g). The resulting white precipitate wascollected by filtration, washed with 2-propanol and then with diethylether, and used without further purification.

The crude sulphonyl chloride (0.16 g, 0.0004 mol) was added to a stirredsolution of 4-(2-aminoethyl)-morpholine (0.156 g, .0.0012 mol) inethanol (40 ml), and the resulting solution stirred at ambienttemperature for 18 hours. The solvent was evaporated under vacuum, theresidue suspended in saturated aqueous sodium carbonate solution (20 ml)and this mixture extracted with dichloromethane (3×20 ml). The organicextracts were combined, dried (Na₂ SO₄) and evaporated under vacuum, andthe resulting residue chromatographed on silica gel (4 g) using amethanol in dichloromethane elution gradient (0-5% methanol).Trituration of the product with diethyl ether gave the title compound asan off-white solid (0.05 g, 25%), m.p. 165°-166° C. Found: C,57.34;H,6.15; N,13.57. C₂₄ H₃₁ N₅ O₅ S requires C,57.46; H,6.23; N,13.96%.

The following seven compounds were obtained from the same sulphonylchloride and the appropriate amine by procedures similar to thatdescribed in Example 1.

EXAMPLE 2

2-[2-Ethoxy-5(4-methyl-l-piperazinylsulphonyl)phenyl]-8-n-propylrido[3,2-d]pyrimidin-4(3H)-one

Obtained using 1-methylpiperazine in 70% yield, m.p. 211°-212° C. Found:C,58.95; H,6.15; N,14.85. C₂₃ H₂₉ N₅ O₄ S requires C,58.58; H,6.20;N,14.85%.

EXAMPLE 3

2- [2-Ethoxy-5-(1-piperazinylsulphonyl]phenyl]-8-n-propylprido[3,2-d]pyrimidin-4(3H) -one

Obtained using piperazine in 43% yield, m.p. 178°-180° C. Found:C,57.66; H,5.96; N,15.40. C₂₂ H₂₇ N₅ O₄ S requires C,57.75; H,5.95;N,15.31%

EXAMPLE 4

2-[2-Ethoxy-5-(4-ethoxycarbonylpiperidinosulphonyl)-phenyl]-8-n-propylprido[3,2-d]pyrimidin-4(3H) -one

Obtained using ethyl isonipecotate in 86% yield, m.p. 204°-205° C.Found: C,59.11; H,6.15; N,10.55. C₂₆ H₃₂ N₄ O₆ S requires C,59.08;H,6.10; N,10.60%.

EXAMPLE 5

2- [2 -Ethoxy-5-(N-2-ethoxycarbonylethyl-N-methyl-sulphamoyl)phenyl]-8-n-propylpyrido[3,2-d]pyrimidin-4(3H)-one

Obtained using ethyl 3- (methylamino) propionate in 67% yield, m.p.145°-146° C. Found: C,57.67; H,6.01; N,11.02. C₂₄ H₃₀ N₄ O₆ S requiresC,57.36; H,6.02; N,11.15%.

EXAMPLE 6

2-[2-Ethoxy-5-(methylsulphamoyl)phenyl]-8-n-propylprido[3,2-d]pyrimidin-4(3H)-one

Obtained using methylamine (in ethanol solution) in 58% yield, m.p.216°-219° C. Found: C,56.81; H,5.68; N,13.52. C₁₉ H₂₂ N₄ O₄ S requiresC,56.70; H,5.51; N,13.92%.

EXAMPLE 7

2-{2-Ethoxy-5-[4-(2-hydroxyethyl)-1-piperazinyl-sulphony]phenyl}-8-n-propylprido[3.2-d ]pyrimidin-4(3H)-one

Obtained using 1-(2-hydroxyethyl) piperazine in 34% yield, m.p.187°-188° C. Found: C, 57.84; H, 6.19; N,13.64. C₂₄ H₃₁ N₅ O₅ S requiresC,57.46; H,6.23; N,13.96%.

EXAMPLE 8

2-{2-Ethoxy-5-[2-(1-imidazolidin-2-onyl)ethyl-sulphamoyl]phenyl}-8-n-propylprido[3,2-d]pryimidin-4(3H)-one

Obtained using 1-(2-aminoethyl)imidazolidin-2-one in 44% yield, m.p.221°-222° C. Found: C,55.69; H,5.63; N,16.55. C₂₃ H₂₈ N₆ O₅ S requiresC,55.18; H,5.64; N,16.79%.

EXAMPLE 9

2-[5-(4-Carboxypiperidinosulphonyl)-2-ethoxyphenyl]-8-n-propylprido[3,2-d]pyrimidin-4(3H)-one

A mixture of2-[2-ethoxy-5-(4-ethoxycarbonyl-piperidinosulphonyl)phenyl]-8-n-propylpyrido[3,2-d]pyrimidin-4(3H)-one(Example 4; 0.55 g, 0.001 mol), potassium hydroxide (0.146 g, 0.0026mol) and ethanol (35 ml) was stirred under reflux for 5 hours, thenallowed to cool. The solvent was evaporated under vacuum, and theresidue chromatographed twice on ion-exchange resin (Bio-rad AG50W-X8H⁺, 27.5 g) using a pyridine in water elution gradient (2-50% pyridine).Crystallisation of the product from aqueous ethanol gave the titlecompound as a colourless solid (0.09 g, 8%), m.p. 262°-264° C. Found:C,57.51; H,5.68; N,11.10. C₂₄ H₂₈ N₄ O₆ S requires C,57.58; H,5.64;N,11.19%.

EXAMPLE 10

2-(2-Ethoxy-5-nitrophenyl)-8-n-propylpyrido[3,2-d]-primidin-4(3H)-one

A solution of2-(2-ethoxyphenyl)-8-n-propylpyrido-[3,2-d]pyrimidin-4(3H)-one(Preparation 8; 0.80 g, 0.0026 mol) in a mixture of concentratedsulphuric acid (5.4 ml) and concentrated nitric acid (0.20 ml) wasstirred at ambient temperature for 4.5 hours. The mixture was thenpoured cautiously into stirred ice/water (50 g) and the resultingmixture extracted with a methanol:dichloromethane mixture (1:9, 3×50ml). The organic extracts were combined, dried (MgSO₄) and evaporatedunder vacuum, and the residue crystallised from ethyl acetate:methanolto give the title compound as an off-white solid (0.71 g, 77%),m.p.257°-259° C. Found: C,61.28; H,5.11; N,15.60. C₁₈ H₁₈ N₄ O₄ requiresC,61.01; H,5.12; N,15.81%.

EXAMPLE 11

2-(5-Amino-2-ethoxyphenyl)-8-n-propylprido[3,2-d]- pyrimidin-4(3H) -one

Stannous chloride dihydrate (2.48 g, 0.011 mol) was added to a stirredsolution of 2-(2-ethoxy-5-nitro-phenyl)-8-n-propylprido[3,2-d]pyrimidin-4(3H)-one (Example 10; 0.78 g, 0.0022 mol) in ethanol(10 ml) and the mixture was heated under reflux for 2 hours, allowed tocool, basified to pH 11 by the addition of 10% aqueous sodium hydroxidesolution, and then extracted with methanol:dichloromethane (1:9, 3×50ml). The organic extracts were combined, dried (MgSO₄) and evaporatedunder vacuum, then the residue was chromatographed on silica gel (12 g)using a methanol in dichloromethane elution gradient (0-2% methanol).Trituration of the product with hexane:ethyl acetate gave the titlecompound as a colourless solid (0.51 g, 71%), m.p. 156°-158° C. Found:C,66.61; H,6.20; N,17.14. C₁₈ H₂₀ N₄ O₂ requires C,66.65; H,6.22;N,17.27%.

EXAMPLES 12 & 12A

2-{2-Ethoxy-5-[(bis-3-pyridylsulphonyl) amino]phenyl}-8-n-propylprido[3,2-d]pyrimidin-4(3H) -one and 2-[2-Ethoxy-5-(3-pyridylsulphonylamino)phenyl]-8-n-propylpyrido [3,2-d]pyrimidin-4(3H) -one

3-Pyridylsulphonyl chloride (0,201 g, 0.00113 mol) was added to astirred mixture of 2-(5-amino-2-ethoxy-phenyl)-8-n-propylprido[3,2-d]pyrimidin-4(3H) -one (Example 11; 0.25 g, 0.00077 mol) andpyridine (5 ml), and the resulting mixture stirred at ambienttemperature for 12 days and then added to water (50 ml). The resultingsolution was acidified to pH 1 with 2N hydrochloric acid, and thenextracted with methanol:dichloromethane (1:9, 3×50 ml). The combinedextracts were dried (MgSO₄) and evaporated under vacuum and the residuechromatographed on silica gel (12 g) using a methanol in dichloromethaneelution gradient (0-2% methanol). Crystallisation of the product fromethyl acetate:methanol gave the first title compound as an off-whitesolid (0.123 g, 34%), m.p. 242°-243° C. Found: C,55.50; H,4.60; N,13.60.C₂₈ H₂₆ N₆ O₆ S₂ requires C,55.43; H,4.32; N,13.85%.

The aqueous phase was extracted further with methanol-dichloromethane(1:9, 3×50 ml), and the combined extracts dried (MgSO₄) and evaporatedunder vacuum. Chromatography of the residue on silica gel (12 g), usinga methanol in dichloromethane elution gradient (2-5% methanol), followedby crystallisation of the product from ethyl acetate:methanol, gave thesecond title compound as a white solid (0.104 g, 29%), m.p. 229°-231° C.Found: C,59.65; H,5.14; N,14.75. C₂₃ H₂₃ N₅ O₄ S requires C,59.34;H,4.98; N,15.04.

EXAMPLE 13

2-[2-Ethoxy-5-(2-propylsulphonylamino) phenyl]-8n-propyl-pyrido[3,2-d]pyrimidin-4(3H)-one

The title compound was prepared using 2-propyl-sulphonyl chloridefollowing the procedure of Example 12 and was obtained as a white solid(55%), m.p. 207°-210° C. Found: C,58.32; H,6.06; N,12.81. C₂₁ H₂₆ N₄ O₄S requires C,58.59; H,6.09; N,13.01%.

EXAMPLE 14

2-[2-Ethoxy-5-(4-methyl-1-piperazinylsulphbonyl)phenyl]-pyrido[3,2-d]pyrimidin-4(3H) -one

2-(2-Ethoxyphenyl)pyrido[3,2-d]pyrimidin-4(3H)-one (Preparation 10; 1.2g, 0.0045 mol) was added portion-wise to stirred chlorosulphonic acid (6ml) under a nitrogen atmosphere at 0° C. The mixture was stirred atambient temperature for 18 hours and then added cautiously to ice/water(100 g). The resulting solution was brought to pH 5 by the addition ofsaturated aqueous sodium carbonate solution and then extracted withdichloromethane methanol (9:1, 3×150 ml). The organic fractions werecombined, dried (MgSO₄) and evaporated under vacuum to give thesulphonyl chloride, which was used without further purification.

The crude sulphonyl chloride (0.55 g, 0.0015 mol) was added to a stirredsolution of 1-methylpiperazine (0.45 g, 0.0045 mol) in ethanol (10 ml),and the resulting solution stirred at ambient temperature for 18 hours.The solvent was evaporated under vacuum and the residue chromatographedon silica gel (10 g), eluting with a mixture ofdichloromethane:methanol: 0.880 aqueous ammonia solution (95:5:1).Crystallisation of the product from ethyl acetate: methanol gave thetitle compound as a white solid (0,325 g, 51%), m.p. 212°-215° C. Found:C,56.03; H,5.44; N,16.55. C₂₀ H₂₃ N₅ O₄ S requires C,55.93; H,5.40;N,16.31%.

The following four compounds were obtained from the same sulphonylchloride and the appropriate amine by procedures similar to thatdescribed in Example 14.

EXAMPLE 15

2-{2-Ethoxy-5[(bis-2-hydroxyethl)sulphamoyl]phenyl}-pyrido[3,2-d]pyrimidin-4(3H)-one

Obtained using diethanolamine in 37% yield, m.p. 223°-225° C. Found:C,52.26; H,4.97; N,13.00. C₁₉ H₂₂ N₄ O₆ S requires C,52.52; H,5.10;N,12.96%.

EXAMPLE 16

2-{2-Ethoxy-5-[(2-pyridylmethyl)sulphamoyl]phenyl}-pyrido[3,2-d]pyrimdin-4(3H)-one

Obtained using 2-aminomethylpyridine in 50% yield, m.p. 230°-231° C.Found: C,57.64; H,4.42; N,16.22. C₂₁ H₁₉ N₅ O₄ S requires C, 57.66; H,4.38; .N, 16.01%.

EXAMPLE 17

2-{2-Ethoxy-5-[(5-isoxazolin-3-onylmethyl)sulphamoyl]-phenyl}pyrido[3,2-d]pyrimidin-4(3H)-one

Obtained using muscimol hydrate in 32% yield, m.p. indeterminate(amorphous solid). Rf 0.40 (dichloromethane: methanol: glacial aceticacid, 90:10:1). Found: C,51.01; H,3.86; N,15.49. C₁₉ H₁₇ N₅ O₆ Srequires C,51.46; H,3.86; N,15.79%.

EXAMPLE 18

2-[5-(5-Amino-3hydroxy-1-pyrazolylsulphonyl)-2-ethoxy-phenyl]pyrido[3,2-d]pyrimidin-4(3H)-one

Obtained using 3-amino-5-hydroxypyrazole in 34% yield, m.p. 246°-249° C.Found: C,50.69; H,3.70; N,19.28. C₁₈ H₁₆ N₆ O₅ S requires C,50.46;H,3.76; N,19.62%.

EXAMPLE 19

2-(2-Ethoxy-5-nitrophenyl)pyrido[3,2-d]pyrimidin-4(3H)-one

A stirred solution of2-(2-ethoxyphenyl)-pyrido[3,2-d]pyrimidin-4(3H)-one (Preparation 10; 1.4g, 0.0052 mol)in concentrated sulphuric acid (11 ml) at 0° C., wastreated dropwise with concentrated nitric acid (0.4 ml). The reactionmixture was allowed to warm to ambient temperature, stirred for afurther 18 hours, then added dropwise to ice/water (70 g). The resultingprecipitate was collected by filtration, dried under vacuum and thencrystallised from acetonitrile to give the title compound as a paleyellow solid (0.22 g, 86%), m.p. 251°-254° C. Found: C,57.69; H,3.87;N,17.94. C₁₅ H₁₂ N₄ O₄ requires C,57.41; H,3.82; N,18.37%.

EXAMPLE 20

2- (5-Amino-2-ethoxyphenyl)pyrido [3,2-d]pyrimidin-4(3H)-one

A stirred mixture of2-(2-ethoxy-5-nitrophenyl)-pyrido[3,2-d]pyrimidin-4(3H)-one (Example 19;1.1 g, 0.00353 mol), stannous chloride dehydrate (4.0 g, 0.0177 mol) andethanol (15 ml) was heated under reflux for 4 hours. The resultingmixture was allowed to cool, diluted with water (15 ml), adjusted to pH8 with 2N aqueous sodium hydroxide solution, vigorously shaken withdichloromethane (30 ml), and then this mixture filtered. The aqueousphase was separated and extracted further with dichloromethane (2×30ml), and the organic extracts were then combined, dried (MgSO₄) andevaporated under vacuum. Crystallisation of the product fromacetonitrile gave the title compound as a hydrated yellow solid (0.72 g,72%), m.p. 208°-210° C. Found: C,62.88; H,4.88; N,19.67. C₁₅ H₁₄ N₄ O₂;0.25H₂ O requires C,62.81; H,5.10; N,19.54%.

EXAMPLE 21

2-[2-Ethoxy-5-(2-propylsulphonylamino)phenyl]pyrido-[3,2-d]pyrimidin-4(3H)-one

The title compound was prepared using 2-propyl-sulphonyl chloride and2-(5-amino-2-ethoxyphenyl)-pyrido[3,2-d]pyrimidin-4(3H)-one (Example20), following the procedure of Example 12, and was obtained as ahydrated solid (59%), m.p. 211°-213° C. Found: C,54.98; H,5.07; N;14.21.C₁₈ H₂₀ N₄ O₄ S;0.25 H₂ O requires C,55.02; H,5.26; N,14.26%.

EXAMPLE 22

2-(5-Isobutyrylamino-2-ethoxphenyl)pyrido[3,2-d]pyrimidin-4(3H)-one

The title compound was prepared using isobutyryl chloride and2-(5-amino-2-ethoxyphenyl) pyrido[3,2-d]pyrimidin-4(3H)-one (Example20), following the procedure of Example 12, and was obtained as a whitesolid (80%), m.p. 256°-259° C. Found:C,64.48; H,5.86; N,15.75. C₁₉ H₂₀N₄ O₃ S requires C,64.76; H,5.72; N,15.90%.

EXAMPLE 23

8-cyano-2-[2-ethoxy-5-(1-piperazinylsulphonyl)phenyl]-pyrido[3,2-d]pyrimidin-4(3H)-one

The title compound was prepared from 8-cyano-2-(2-ethoxyphenyl )pyrido[3,2-d]pyrimidin-4(3H)-one (Preparation 14) and piperazine,following the procedure of Example 1, and was obtained as an off-whitesolid (22%), m.p. 172°-175° C. Found: C,54.09; H,4.70; N,18.71. C₂₀ H₂₀N₆ O₄ S requires C,54.53; H,4.58; N, 19 . 08%.

EXAMPLE 24

8-Cyano-2-[2-ethoxy-5-(4-methyl-1-piperazinyl-sulphonyl)phenyl]pyrido[3,2d]pyrimidin-4(3H)-one

The title compound was prepared from 8-cyano-2-(2-ethoxyphenyl)pyrido[3,2-d]pyrimidin-4(3H)-one (Preparation 14 ) and1-methylpiperazine, following the procedure of Example 1, and wasobtained as an off-white solid (8%), m.p. 239°-240° C. Found: C,55.61;H,4.93; N,18.60. C₂₁ H₂₂ N₆ O₄ S requires C,55.49; H,4.88; N,18.49%.

EXAMPLE 25

8-Carbamoyl -2-[2-ethoxy-5-(4-methyl-1-piperazinyl-sulphonyl)phenyl]pyrido[3,2-d]pyrimidin-4(3H)-one

The title compound was prepared from 8-carbamoyl-2-(2-ethyoxyphenyl)pyrido[3,2-d]pyrimidin-4(3H)-one (Preparation 16) and1-methylpiperazine, following the procedure of Example 1, and wasobtained as a solvated white powder (13%), m.p. 237°-238° C. Found:C,49.86; H,4.93; N,16.14. C₂₁ H₂₄ N₆ O₅ S;0.60 CH₂ Cl₂ requires C,49.69;H,4.75; N.16.12%.

PREPARATION 1

Diethy14-n-propylpyridine-2,3,-dicarboxylate

A solution of diethyl 3-chloro-2-oxosuccinate (137.4 g, 0.69 mol),hexen-2-al (72.5 g, 0.74 mol) and ammonium sulphamate (190.2 g, 1.66mol) in ethanol (450 ml) was stirred under reflux for 36 hours and thenfiltered. The filtrate was evaporated under vacuum, the resultingresidue dissolved im water (500 ml) and this solution extracted withethyl acetate (6×500 ml). The combined organic extracts were dried(MgSO₄) and evaporated under vacuum, then the resulting residue waschromatographed on silica gel (50 g), using an ethyl acetate in hexaneelution gradient (0-20% ethyl acetate), to give the title compound as anorange oil (34.1 g, 21%). Rf 0.20 (ethyl acetate:hexane, 20:80).

PREPARATION 2

4-n-Propylpyridine-2,3-dicarboxamide

A mixture of liquid ammonia (40 ml) and diethyl4-n-propylpyridine-2,3-dicarboxylate (Preparation 1; 2.0 g, 0.0075 mol)was heated in an autoclave at 100° C. for 18 hours and then allowed tocool. The ammonia was allowed to evaporate, then the residue wasazeotroped with methanol and crystallised from ethyl acetate: methanolto give the title compound as a colourless solid (0.1 g, 6.4%), m.p.178°-179° C. Found: C,57.73; H,6.45; N,19.85. C₁₀ H₁₃ N₃ O₂ requiresC,57.96; H,6.32; N,20.28%.

PREPARATION 3

7-n-Propyl-4-azaphthalimide

A stirred solution of 4-n-propylpyridine-2,3-dicarboxamide (Preparation2; 0.1 g, 0.00048 mol) in N,N-dimethylacetamide (10 ml) was heated at160° C. for 5 hours and then the solvent was evaporated under vacuum.The residue was purified by chromatography on silica gel (5 g), elutingwith a solution of 3% methanol in dichloromethane, followed bycrystallisation from ethyl acetate to give the title compound as a lightyellow solid (0.014 g, 15%), m.p. 163°-165° C. Found: C,63.41; H,5.35;N,15.04. C₁₀ H₁₀ N₂ O₂ requires C,63.15; H,5.30; N,14.73%.

PREPARATION 4

3-Amino-4-n-propylpyridine-2-carboxylic acid

A stirred solution of 7-n-propyl-4-azaphthalimide (Preparation 3; 1.9 g,0.010 mol) in aqueous sodium hydroxide solution (2.8 g, 0.07 mol of NaOHin 30 ml of water) was treateed with aqueous sodium hypochloritesolution (5 ml, 0.010 mol). The resulting mixture was heated at 80° C.for 0.5 hour, cooled and acidified with dilute sulphuric acid (50%, 2ml). The suspension produced was filtered and the solid thus obtainedwas crystallised from water to give the title compound as an off-whitesolid (0.38 g, 21%), m.p. 185°-188° C. Found: C,59.34; H,6.63; N,15.35.C₉ H₁₂ N₂ O₂ requires C,59.98; H,6.71; N,15.55%.

PREPARATION 5

Ethyl 3-amino-4-n-propylpyridine-2-carboxylate

3-Amino-4-n-propylpyridine-2-carboxylic acid (Preparation 4; 0.36 g,0,002 mol) was added to a stirred mixture of cesium carbonate (0,325 g,0.001 mol) in water (20 ml), then this mixture was evaporated undervacuum and the residue azeotroped with dimethylformamide (2×20 ml). Theresulting cesium salt was suspended in dimethylformamide (3 ml) and thestirred suspension then treated dropwise with ethyl iodide (0.17 ml,0.0021 mol). After a further 0.25 hour, the solvent was evaporated undervacuum and the residue partitioned between water (20 ml) and ethylacetate (20 ml). The organic phase was washed with water (10 ml), dried(MgSO₄) and evaporated under vacuum, then the residue crystallised fromacetone:hexane to give the title compound as an off-white solid (0.35 g,84%), m.p. 93°-96° C. Found: C,63.39; H,7.73; N,13.39. C₁₁ H₁₆ N₂ O₂requires C,63.44; H,7.74; N,13.45%.

PREPARATION 6

3-Amino-4-n-propylpyridine-2-carboxamide

A mixture of ethyl 3-amino-4-n-propylpyridine-2-carbolate (Preparation5; 7.4 g, 0.035 mol) and liquid ammonia (60 ml) was heated in anautoclave at 00° C for 18 hours. The mixture was allowed to cool and theammonia to evaporate, then the residue was crystallised from methanol togive the title compound as a colourless solid (4.84 g, 76%), m.p.139°-141° C. Found: C,60.32; H,7.27; N,23.56. C₉ H₁₃ N₃ O requiresC,60.31; H,7.31; N,23.45%.

PREPARATION 7

3-(2-Ethoxybenzoylamino)-4-n-propylpyridine-2-carboxamide

2-Ethoxybenzoyl chloride (2.96 g, 0.016 mol) was added dropwise to astirred solution of 3-amino-4-n-propylpridine-2-carboxamide (Preparation6; 1.43 g, 0.008 mol) in pyridine (40 ml) at 0° C. The mixture wasstirred at ambient temperature for 4 hours and then the solventevaporated under vacuum. The residue was dissolved in dichloromethane(100 ml), the solution washed with saturated aqueous sodium carbonatesolution (100 ml) and the aqueous phase then washed with dichloromethane(2×25 ml). The combined organic extracts were dried (MgSO₄) andevaporated under vacuum, then the residue purified by chromatography onsilica gel (15 g), using a methanol in dichloromethane elution gradient(0-3% methanol), followed by crystallisation from ethyl acetate to givethe product as a light brown solid (1.36 g, 60%), 129°-131° C. Found:C,66.29; H,6.53; N,12.78. C₁₈ H₂₁ N₃ O₃ requires C,66.04; H,6.47;N,12.84%.

PREPARATION 8

2-(2-Ethoxyphenyl)-8-n-propylpyrido[3,2-d]pyrimidin-4(3H)-one

A mixture of 3-(2-ethoxybenzoylamino)-4-n-propylpridine-2-carboxamide(Preparation 7; 1.52 g, 0.0046 mol) and anhydrous zinc chloride (1.88 g,0.014 mol) was heated at 210° C. for 0.25 hour. The cool mixture wasdissolved in methanol (20 ml) and this solution poured into an aqueoussolution of disodium ethylenediamine tetraacetic acid (10.3 g in 200 mlwater). The resulting mixture was basified with saturated aqueous sodiumcarbonate solution (20 ml), then extracted with dichloromethane (4×60ml). The combined organic extracts were dried (MgSO₄) and evaporatedunder vacuum, then the residue crystallised from ethyl acetate to givethe title compound as a white solid (0.92 g, 65%), m.p. 134°-137° C.Found: C,69.69; H,6.27; N,13.54. C₁₈ H₁₉ N₃ O₂ requires C,69.88; H,6.19;N,13.58%.

PREPARATION 9

3-(2-Ethoxybenzoylamino)pyridine-2-carboxamide

The title compound was prepared from 2-ethoxybenzoyl chloride and3-aminopyridine-2-carboxamide (J. Chem. Soc., 1956, 1045) following theprocedure of Preparation 7 and was obtained as an off-white solid (100%), m.p. 172°-177° C. Found: C,62.91; H,5.30; N,14.51. C₁₅ H₁₅ N₃ O₃requires C,63.15; H,5.30; N,14.73%.

PREPARATION 10

2-(2-Ethoxyphenyl)pyrido[3,2-d]pyrimidin-4(3H)-one

The title compound was prepared from 3-(2-ethoxybenzoylamino)pyridine-2-carboxamide (Preparation 9) following the procedure ofPreparation 8 and was obtained as an off-white solid (56%), m.p.184°-187° C. Found: C, 67.24; H, 4.87; N, 15.76. C₁₅ H₁₃ N₃ O₂ requiresC,67.40; H,4.90; N,15.72%.

PREPARATION 11

Ethyl 3-amino-4-cyanopyridine-2-carboxylate

A stirred solution of ethyl 2-cyano-2-(formylamino)acetate J. Org.Chem., 1979, 44, 3835; 0.47 g, 0.003 mol), acrylonitrile (1.2 ml, 0.018mol) and trifluoroacetic acid (0.02 ml, 0.0003 mol) in1,2-dichloroethane (4 ml) was heated under reflux for 3 days. Thesolvent was removed by evaporation under vacuum, the residue dissolvedin dichloromethane (30 ml) and the resulting solution washed withsaturated aqueous sodium bicarbonate solution (30 ml). The aqueous phasewas washed with dichloromethane (30 ml) and the organic solutions thencombined, dried (MgSO₄) and evaporated under vacuum. Chromatography ofthe residue on silica gel (12 g), eluting with dichloromethane:methanol(100:1), followed by crystallisation from acetone: hexane, gave thetitle compound as a colourless solid (0.12 g, 21%), m.p. 114°-116° C.Found: C,56.89; H,4.75; N,22.08. C₉ H₉ N₃ O₂ requires C,56.54; H,4.75;N,21.98%.

PREPARATION 12

3-Amino-4-cyanopyridine-2-carboxamide

A mixture of liquid ammonia (30 ml) and ethyl3-amino-4-cyanopyridine-2-carboxylate (Preparation 11; 2.8 g, 0.0147mol) was heated at 100° C. in an autoclave for 18 hours. The ammonia wasallowed to evaporate and the resulting product crystallised from ethylacetate to give the title compound as an off-white solid (2.2 g, 94%),m.p. >310° C. Found: C,51.84; H,3.69; N,34.30. C₇ H₆ N₄ O requiresC,51.85; H,3.73; N,34.56%.

PREPARATION 13

4-Cyano-3-(2-ethoxybenzylamino)pyridine-2-carboxamide

The title compound was prepared from 2-ethoxybenzoyl chloride and3-amino-4-cyanopyridine-2-carboxamide (Preparation 12), following theprocedure of Preparation 7, and was obtained as a colourless solid.(6.2%), m.p. 150°-152° C. Found: C,61.99; H,4.62; N,17.84. C₁₆ H₁₄ N₄ O₃requires C,61.93; H,4.55; N,18.06%.

PREPARATION 14

8-Cyano-2-(2-ethoxyphenyl)pyrido[3,2-d]pyrimidin-4(3H)-one

The title compound was prepared from 4-cyano-3-(2-ethoxybenzoylamino)pyridine-2-carboxamide (Preparation 13), following the procedure ofPreparation 8, and was obtained as a white solid (54%), m.p. 255°-256°C. Found: C,66.03; H,4.10; N,19.08. C₁₆ H₁₂ N₄ O₂ requires C,65.75;H,4.14; N,19.17%.

PREPARATION 15

8-Carbamoyl-2-(2-ethoxyphenyl)pyrido[3,2-d]pyrimidin-4(3H)-one

30% Aqueous hydrogen peroxide solution (0.5 ml) was added to a stirredaqueous sodium hydroxide solution (1M, 40 ml), followed by8-cyano-2-(2-ethoxyphenyl)pyrido[3,2-d]pyrimidin-4(3H)-one (Preparation14; 0.2 g, 0.00068 mol) and ethanol (2 ml). The mixture was heated underreflux for 2 hours, allowed to cool, acidified with 1N hydrochloricacid, and then extracted with a mixture of dichloromethane and methanol(10:1, 5×50 ml). The combined organic fractions were evaporated undervacuum and the resulting residue triturated with ethanol to give thetitle compound as a colourless solid (0.152 g, 72%), m.p. 295°-297° C.Found: C,61.65; H,4.56; N,17.61. C₁₆ H₁₄ N₄ O₃ requires C,61.93; H,4.55;N,18.06%.

Biological activity

The following Table illustrates the in vitro activities for a range ofthe compounds of the invention.

                  TABLE                                                           ______________________________________                                        IN VITRO PDE INHIBITORY DATA:                                                 SELECTIVITY BETWEEN CALCIUM/CALMODULIN                                        (Ca/CAM)-INDEPENDENT cGMP PDE AND cGMP-                                       INHIBITED cAMP PDE                                                                   IC.sub.50 (nM) SELECTIVITY                                             EXAMPLE  cGMP      cAMP       RATIO                                           ______________________________________                                        1        21        19,000     904                                             2        26        13,000     500                                             4        5.6        7,600     1,357                                           5        14         8,300     592                                             7        9.8       11,000     1,122                                           9        1.2         220      183                                             .sup. 12A                                                                              19         4,600     242                                             24       25        >100,000   >4,000                                          ______________________________________                                    

Safety Profile

Examples 7 and 9 have been tested at doses of up to 0.1 mg/kg and 1mg/kg i.v. respectively, Examples 1 and 8 at doses of up to 3 mg/kg i.d.and Example 3 at doses of up to 10 mg/kg i.d., in rabbit, with nountoward effects being observed.

We claim:
 1. A compound of formula (I): ##STR9## or a pharmaceuticallyacceptable salt thereof, wherein R¹ is H, C₁ -C₄ alkyl, CN or CONR⁴ R⁵;R² is C₂ -C₄ alkyl; R³ is SO₂ NR⁶ R⁷, NO₂, N₂, NHCOR⁸, NHSO₂ R⁸ orN(SO₂ R⁸)₂ ; R⁴ and R⁵ are each independently selected from H and C₁ -C₄alkyl; R⁶ and R⁷ are each independently selected from H and C₁ -C₄ alkyloptionally substituted with CO₂ R⁹, OH, pyridyl, 5-isoxazolin-3-onyl,morpholino or 1-imidazolidin-2-onyl; or together with the nitrogen atomto which they are attached form a pyrrolidino, piperidino, morpholino,1-pyrazolyl or 4-(NR¹⁰)-1-piperazinyl group wherein any of said groupsmay optionally be substituted with one or two substituents selected fromC₁ -C₄ alkyl, CO₂ R⁹, NH₂ and OH; R⁸ is C₁ -C₄ alkyl or pyridyl; R⁹ is Hor C₁ -C₄ alkyl; and R.sup.° is H, C₁ -C₄ alkyl or (hydroxy)C₂ -C₃alkyl.
 2. A compound according to claim 1 wherein R¹ is H, n-propyl, CNor CONH₂ ; R² is ethyl; R³ is SO₂ NR⁶ R⁷, NO₂, NH₂, NHCOCH(CH₃)₂, NHSO₂CH(CH₃)₂, NHSO₂ (3-pyridyl) or N[SO₂ (3-pyridyl)]₂ ; R⁶ is H, methyl or2-hydroxyethyl; R⁷ is methyl optionally substituted with 2-pyridyl or5-isoxazolin-3-onyl, or ethyl 2-substituted with OH, CO₂ CH₂ CH₃,morpholino or 1-imidazolidin-2-onyl, or R⁶ and R⁷ together with thenitrogen atom to which they are attached form a ( 4-CO₂ R⁹) piperidino,5-amino-3-hydroxy-1-pyrazolyl or 4-(NR¹⁰)-1-piperazinyl group; R⁹ is Hor ethyl; and R.sup. is H, methyl or 2-hydroxyethyl.
 3. A compoundaccording to claim 2 wherein R¹ is n-propyl or CN; R² is ethyl; R³ isSO₂ NR⁶ R⁷, NHSO₂ CH(CH₃)₂, NHSO₂ (3-pyridyl) or N[SO₂ (3-pyridyl)]₂ ;R⁶ is H or methyl; R⁷ is methyl, or ethyl 2-substituted with CO₂ CH₂CH₃, morpholino or 1-imidazolidin-2-onyl, or R⁶ and R⁷ together with thenitrogen atom to which they are attached form a (4-CO₂ R⁹)piperidino or4- (NR¹⁰) -1-piperazinyl group; R⁹ is H or ethyl; and R¹⁰ is H, methylor 2-hydroxyethyl.
 4. A compound according to claim 3 wherein the saidcompound of formula (I) is selectedfrom2-[2-ethoxy-5-(4-ethoxycarbonylpiperidino-sulphonyl)phenyl]-8-n-propylpyrido[3,2-d]pyrimidin-4(3H)-one;2-[5-(4-carboxypiperidinosulphonyl)-2-ethoxyphenyl]-8-n-propylpyrido[3,2-d]pyrimidin-4(3H)-one;2-{2-ethoxy-5-[4-(2-hydroxyethyl)-1-piperazinyl-sulphonyl]phenyl}-8-n-propylpyrido[3,2-d]pyrimidin-4(3H)-onep1 and2-{2-ethoxy-5-[(bis-3-pyridylsulphonyl)amino]-phenyl}-8-n-propylpyrido[3,2-d]pyrimidin-4(3H)-one.5. A pharmaceutical composition comprising a compound of formula (I), ora pharmaceutically acceptable salt thereof, according to claim 1,together with a pharmaceutically acceptable diluent or carrier.
 6. Amethod of treating or preventing stable, unstable and variant(Prinzmetal) angina, hypertension, pulmonary hypertension, congestiveheart failure, atherosclerosis, stroke, peripheral vascular disease,conditions of reduced blood vessel patency, chronic asthma, bronchitis,allergic asthma, allergic rhinitis, glaucoma or diseases characterizedby disorders of gut motility, in a mammal, which comprises administeringto said mammal a therapeutically effective amount of a compound offormula (I), or a pharmaceutically acceptable salt thereof, or apharmaceutical composition containing either entity, according toclaim
 1. 7. A method of treating or preventing stable, unstable andvariant (Prinzmetal) angina, hypertension, pulmonary hypertension,congestive heart failure, atherosclerosis, stroke, peripheral vasculardisease, conditions of reduced blood vessel patency, chronic asthma,bronchitis, allergic asthma, allergic rhinitis, glaucoma or diseasescharacterized by disorders of gut motility, in a mammal, which comprisesadministering to said mammal a therapeutically effective amount of acompound of formula (I), or a pharmaceutically acceptable salt thereof,or a pharmaceutical composition containing either entity, according toclaim
 5. 8. A compound of formula (III): ##STR10## wherein Z is halo; R¹is H, C₁ -C₄ alkyl, CN or CONR⁴ R⁵ ; R² is C₂ -C₄ alkyl; and R⁴ and R⁵are each independently selected from H and C₁ -C₄ alkyl.
 9. A compoiundof formula (II): ##STR11## wherein R¹ is CN or CONR⁴ R⁵ ; R² is C₂ -C₄alkyl; andR⁴ and R⁵ are each independently selected from H and C₁ -C₄alkyl.